Need a 12V guru for a project

[Crymson]

Hi Beyond. I need some 12v help for a camping project i'm working. Any experts here or any shops you'd recommend? Maybe a good marine place?

[Graham_A_M]

www.the12volt.com that should answer any questions you have. OTherwise post them here and we'll do our best to help.

[Crymson]

Well, i'm picking up a 4x4 trailer for camping and want to build an electrical system into it. Something that can be used to run a water pump for a water tank in the trailer, an inverter to run some lights/music etc off of 120v, and a deep cycle batter that can be charge by some beefy solar panels (i'm thinking a 140watt 2 panel setup) when parked or the truck while running, or an onsite generator if available.

[Graham_A_M]

So you basically need a wiring schematic drawn up for everything?

[Crymson]

Yeah -- but I could probably figure that out assuming i could get off the shelf components for the electrical panel and charging system.

At this point, i'm more concerned with component selection and fit for purpose stuff ie - will the battery charge with that solar setup, what AH rated battery do i need, etc. etc.

[tsi_neal]

None of what your trying to do is hard to figure out.. Canadian tire will have 100% of what you need if your wanting / willing to get the "economical" parts (in a case like this i see no reason not to)

W x V = A

figure what all your loads are going to be in one unit, probably watts will work best (use the above formula, and get specs for all the items you want to run) Get enough batteries that you wont run out of power overnight and enough solar panels to recharge the batteries in the day.

I would assume that mid summer you will have 10-12 hours of strong enough sun to charge the batteries

[Crymson]

ha! you mean watts = v * amps. I'm not THAT much of a newbie.

[Tik-Tok]

Originally posted by tsi_neal

W x V = A


100W bulb x 110V = 11,000 amperes :eek: I'm never changing a light bulb again!

[tsi_neal]

LOL, small mistake... But really take a few minutes and do some math, sizing components for applications like this is pretty easy.

[UndrgroundRider]

Honestly, for a system like that if you connect a red wire to a red post, you're golden.

You will need a charge controller for the battery to prevent over charging by the panels. If you wanted to be safe you could fuse the line to the water pump, and the power inverter if you will be connecting some big accessories. Do plan on storing the batteries outside, since they can produce gasses.

Calculating the AH rating needed is fairly straight forward.

Easiest way is to tally up AH consumption in a day. So, figure your lights from 6PM to 2AM (ish). Accessories intermittent throughout the day, and whatever else you have planned. For example, say you had two 60watt lights running. That's 120watts total, divide by 12, that's 10amps, times 8 hours that's 80AH for the lights in a given day. Assume you will be listening to music for the same amount of time as the lights, and a light stereo is about 30watts, so 2.5 amps, times 8 hours is 20AH.

The water pump is probably insignificant, since it will be on only for seconds at a time. I don't even know if I'd bother factoring that in. If you're going to charge a laptop once a day, that's 50watts over an hour or two. That's 4.1 amps, times 2 hours is 8.2AH.

Total all in is 128.2AH. You probably want to figure for 30-50% more than that number. Keep in mind you don't have to buy 1 big battery with that rating, you can buy two smaller batteries and run them in parallel.

In Alberta in September daylight is 13.5 hours. So we will need to produce 9.5amps of electricity per hour. That's 114 watts. However keep in mind solar panels will only produce their rated wattage in direct sunlight, and during the morning and evening hours you might even see 10% of the rated wattage. I would try it with your planned two panels, and if you find you're running out of juice add a second panel. The real test will be the rainy days.

Sunlight during the other summer months is longer, so you might be fine. Also keep in mind that all of the can tire charge controllers are 7.5 amps, which is too low. 140 watts is 11.6 amps, so you will need something beefier.


Of course that whole system is over engineered. If you get power efficient lights your energy consumption will drop dramatically. Truth be told you probably won't be charging a laptop every day, and one of those portable iPod dock stereos will probably consume less than 30 watts. Plus, you probably won't be running your lights for 8 hours a day since they will attract the bugs. Only you can work out exactly what you will be doing, but this is a good guideline.

[Crymson]

That's the post i was looking for.

Been doing alot of work on solar charger controllers. Canadian tire has a 30A 500watt with good readout on it that i'll probably use.

For lighting, I was going to use LED ropelights. depending on the spacing of the LED's, the max is about 1 watt/foot. and 20 feet of that stuff puts out quite a bit of usealbe light, it's alos very easy to string over trees, around the insides of awnings, and under the guide wires for tarp cities. Very handy stuff.

30 watts for music is probably low, we'll up that.

I also want to try and get a small portable freezer/fridge that would be great. but i suspect the wattage on those is high.

[spike98]

Originally posted by Crymson
That's the post i was looking for.

Been doing alot of work on solar charger controllers. Canadian tire has a 30A 500watt with good readout on it that i'll probably use.

For lighting, I was going to use LED ropelights. depending on the spacing of the LED's, the max is about 1 watt/foot. and 20 feet of that stuff puts out quite a bit of usealbe light, it's alos very easy to string over trees, around the insides of awnings, and under the guide wires for tarp cities. Very handy stuff.

30 watts for music is probably low, we'll up that.

I also want to try and get a small portable freezer/fridge that would be great. but i suspect the wattage on those is high.

There is always the electric coolers that you see at can-tire. They dont take as much juice as a full blown mini fridge and you can pack them with ice to keep the power consumption low.

To charge while running put an isolator inline to your battery bank from the alternator. For good measure put a circut breaker right after. Use 0 gauge welding cable for your major lines. Its cheap and very robust.